Cmp slurry mix and delivery system

ABSTRACT

A CMP slurry mix and delivery system includes at least one container for holding a polishing agent; a pump connected to the container for pumping the polishing agent to a point of use; and a slurry dispersion unit installed between the pump and the point of use, wherein slurry dispersion unit provides megasonic energy that is capable of dispersing the polishing agent flowing through the slurry dispersion unit.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the field of chemical mechanical polishing or chemical mechanical planarization (CMP) techniques. More particularly, the present invention relates to a slurry mix and delivery system for a CMP apparatus.

2. Description of the Prior Art

As known in the art, mechanical polishing or chemical mechanical planarization (CMP) is essential to the semiconductor fabrication to achieve a high degree of planarity on the surface of a semiconductor wafer. In a CMP process, the wafer is typically pressed against a rotating polishing pad. The wafer may rotate and oscillate over the surface of the polishing pad to improve polishing effectiveness. During the CMP process, aqueous slurry is provided to facilitate the polishing process.

Typically, the aqueous slurry is introduced from a slurry reservoir through a piping system to a nozzle or sprayer where it is applied to the polishing pad to subsequently contact the wafer polishing surface. Alternatively, the slurry may be fed through a feed system directly through the lower portion of the polishing pad. The aqueous slurry may include abrasive particles, a reactive chemical agent such as a transition metal chelated salt or an oxidizer, and adjuvants such as solvents, buffers, and passivating agents.

One problem associated with the conventional CMP techniques is the agglomeration of the slurry particles. Micro-scratching or other damage occurs to the wafer surface during polishing when the slurry particles or agglomerate exceed a given size. Therefore, a need exists in the industry to provide an improved slurry mix and delivery system for a CMP apparatus, which is capable of avoiding agglomeration of the slurry particles or dispersing agglomerated particles, thereby maintaining good particle dispersion in the slurry stream.

SUMMARY OF THE INVENTION

It is one object of the present invention to provide an improved slurry mix and delivery system for a CMP apparatus in order to solve the above-described problems.

To these ends, according to one aspect of the present invention, there is provided a CMP slurry mix and delivery system including at least one container for holding a polishing agent; a pump connected to the container for pumping the polishing agent to a point of use; and a slurry dispersion unit installed between the pump and the point of use, wherein slurry dispersion unit provides megasonic energy that is capable of dispersing the polishing agent flowing through the slurry dispersion unit.

According to one aspect of the claimed invention, the slurry dispersion unit comprises a megasonic tank that is filled with a fluid, and a spiral tube installed within the megasonic tank and is dipped into the fluid. The polishing agent flows through the spiral tube. The number of turns of the spiral tube can be determined by the retention time of the polishing agent flowing through the spiral tube within the megasonic tank. The slurry dispersion unit may further comprise a transducer coupled to the fluid held by the megasonic tank and the polishing agent flowing through the spiral tube.

These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings:

FIG. 1 is a schematic diagram illustrating a CMP slurry mix and delivery system in accordance with one embodiment of this invention;

FIG. 2 is a schematic, perspective view showing an exemplary megasonic tank of the CMP slurry mix and delivery system in accordance with one embodiment of this invention; and

FIG. 3 is a schematic, cross-sectional diagram illustrating an exemplary CMP station or CMP polishing unit in accordance with one embodiment of this invention.

It should be noted that all the figures are diagrammatic. Relative dimensions and proportions of parts of the drawings have been shown exaggerated or reduced in size, for the sake of clarity and convenience in the drawings. The same reference signs are generally used to refer to corresponding or similar features in modified and different embodiments.

DETAILED DESCRIPTION

In the following description, numerous specific details are given to provide a thorough understanding of the invention. However, it will be apparent to one skilled in the art that the invention may be practiced without these specific details. In order to avoid obscuring the present invention, some well-known system configurations and process steps are not disclosed in detail.

Likewise, the drawings showing embodiments of the apparatus are semi-diagrammatic and not to scale and, particularly, some of the dimensions are for the clarity of presentation and are shown exaggerated in the figures. Also, where multiple embodiments are disclosed and described having some features in common, for clarity and ease of illustration and description thereof like or similar features one to another will ordinarily be described with like reference numerals.

FIG. 1 is a schematic diagram illustrating a CMP slurry mix and delivery system in accordance with one embodiment of this invention. As shown in FIG. 1, the CMP slurry mix and delivery system 10 comprises a plurality of container 12 and 14 each of which can hold a fluid constituent used for the slurry. Although two containers 12 and 14 for two-liquid mixed type slurry are shown, fewer or more containers can be provided depending on the composition of the slurry to be used in the CMP process. For example, in a case that the slurry is pre-mixed, only one container is needed.

According to the embodiment of this invention, the first container 12, which holds a first polishing agent S1, is connected to a first pump P1 via a conduit 101. The second container 14, which holds a second polishing agent S2, is connected to a second pump P2 via a conduit 102. The first polishing agent S1 is pumped to a main slurry conduit 105 via a conduit 103 and mixed with the second polishing agent S2 pumped by the second pump P2 via the conduit 104. The mixed slurry S3 then flows through a slurry dispersion unit 20 and is well dispersed therein. The dispersed slurry S4 is then pumped into a CMP station 30 via a conduit 106 and is sprayed onto a polishing pad by a slurry feeding device.

As used herein, the term “polishing agent” may include one or more fluids that are used during a CMP or other wafer polishing process. Examples of polishing agents include but not limited to slurries, buffing agents, and cleansing agents, among others. A polishing agent may include one or more constituents.

FIG. 2 is a schematic, perspective view showing an exemplary slurry dispersion unit of the CMP slurry mix and delivery system in accordance with one embodiment of this invention. As shown in FIG. 2, the slurry dispersion unit 20 comprises a megasonic tank 201 that is filled with fluid 202 such as water or pure water. A spiral tube 210 is disposed within the megasonic tank 201 and is dipped into the fluid 202. The number of turns of the spiral tube 210 can be determined by the retention time of the mixed slurry S3 flowing through the spiral tube 210 within the megasonic tank 201. One end of the spiral tube 210 may be coupled to a sidewall of the megasonic tank 201 via an inlet joint 205 that is connected to the main slurry conduit 105. The other end of the spiral tube 210 may be coupled to an opposite sidewall of the megasonic tank 201 via an outlet joint 206 that is connected to the conduit 106. The spiral tube 210 may be made of plastic materials such as polyvinyl chloride (PVC), metal such as copper, silicone or any suitable materials.

According to the embodiment of this invention, the megasonic tank 201 may be equipped with a transducer 230, which may be coupled to the fluid 202 held by the megasonic tank 201 and the slurry flowing through the spiral tube 210. For example, the transducer 230 may oscillate between compressed and strained states at a near 1 MHz rate. The megasonic oscillation output by the transducer 230 causes a megasonic pressure oscillation within the megasonic tank 201, thereby dispersing the slurry flowing through the spiral tube 210. Optionally, a heater such as a thermal couple may be installed within the megasonic tank 201 to alter the temperature of the fluid 202 as well as the temperature of the slurry flowing through the spiral tube 210. The transducer 230 and the heater 240 may be connected to a controller (not shown). The agglomerated particles in the slurry stream can be effectively dispersed by megasonic energy provided by the slurry dispersion unit 20.

As previously described, the dispersed slurry S4 is then pumped into the CMP station 30 and is sprayed onto a polishing pad by a slurry feeding device. As shown in FIG. 3, the CMP station 30 may comprise a platen 300 connected to a shaft 301 for rotating the platen 300 about its central axis during polishing. A polishing pad 310 is mounted on the platen 300. A wafer 322 is held and rotated by a carrier 320. In polishing, a slurry feeding device 330 receives the dispersed slurry S4 and sprays slurry S4 onto the polishing pad 310. The rotating wafer 322 is pressed against the polishing pad 310 by the carrier 320 to cause relative movement between the polishing surface of the polishing pad 310 and the wafer 322, thereby producing a combined mechanical and chemical effect on the surface of the wafer.

According to another embodiment of this invention, the first polishing agent S1 and the second polishing agent S2 may be mixed and dispersed within the megasonic tank 201 by megasonic energy. In such case, the fluid 202 and the spiral tube 210 are omitted. Further, the megasonic tank 201 may be hermetic or airtight. An additional pump (not shown) may be disposed in the conduit 106 to control the flow rate of the slurry S4.

Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. 

1. A CMP slurry mix and delivery system, comprising: at least one container for holding a polishing agent; a pump connected to the container for pumping the polishing agent to a point of use; and a slurry dispersion unit installed between the pump and the point of use, wherein slurry dispersion unit provides megasonic energy that is capable of dispersing the polishing agent flowing through the slurry dispersion unit.
 2. The CMP slurry mix and delivery system according to claim 1 wherein the slurry dispersion unit comprises a megasonic tank that is filled with a fluid.
 3. The CMP slurry mix and delivery system according to claim 2 wherein the fluid does not contact with the polishing agent.
 4. The CMP slurry mix and delivery system according to claim 2 wherein the fluid comprises water.
 5. The CMP slurry mix and delivery system according to claim 4 wherein the fluid is pure water.
 6. The CMP slurry mix and delivery system according to claim 2 wherein the slurry dispersion unit further comprises a spiral tube dipped into the fluid, and wherein the polishing agent flows through the spiral tube.
 7. The CMP slurry mix and delivery system according to claim 6 wherein the spiral tube is made of plastic materials, metal, or silicone.
 8. The CMP slurry mix and delivery system according to claim 6 wherein number of turns of the spiral tube is determined by a retention time of the polishing agent flowing through the spiral tube within the megasonic tank.
 9. The CMP slurry mix and delivery system according to claim 6 wherein the slurry dispersion unit further comprises a transducer coupled to the fluid held by the megasonic tank and the polishing agent flowing through the spiral tube.
 10. The CMP slurry mix and delivery system according to claim 6 wherein the slurry dispersion unit further comprises a heater for altering temperature of the fluid as well as temperature of the polishing agent flowing through the spiral tube. 